Image Resizer
Process images in your browser — your files never leave your device.
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What is the Image Resizer?
This tool changes an image's pixel dimensions — by exact width and height, or by percentage — and re-exports it as JPG, PNG or WebP at a quality you choose. With aspect ratio locked, changing the width automatically recalculates the height (or vice versa) so the image scales proportionally with no distortion. Unlock it and you can set width and height independently, which stretches the image to exactly fill that box — useful for a fixed banner slot, but it will visibly distort anything that doesn't already match the target ratio. There is no separate crop-to-fill mode here; if you need to fill a box without stretching, crop first.
Resizing and compressing solve different problems. Resizing changes the pixel grid — a 4000×3000 photo becomes 1200×900, say — which shrinks file size as a side effect of having fewer pixels to store. Compressing keeps the same pixel grid and squeezes the encoding instead. For the smallest possible file, do both: resize down to the dimensions you actually need, then compress the result.
Why use a free image resizer?
Resize by exact pixels or by percentage
Switch between typing a target width/height and scaling by a percentage of the original — useful when you know the exact output size you need versus when you just want it "half as big."
Aspect ratio lock prevents accidental distortion
With the lock on, editing width recalculates height (and vice versa) automatically, so you can never accidentally stretch a photo out of shape while resizing.
Choose the output format on the way out
Export the resized image as JPG, PNG or WebP regardless of the source format, with a quality slider for the lossy formats.
High-quality resampling
Resizing uses the browser's high-quality image smoothing rather than nearest-neighbour scaling, so downscaled photos stay sharp rather than looking pixelated or aliased.
Nothing uploaded
Resizing runs entirely in your browser via the Canvas API — your image is never sent to a server.
How do you use the Image Resizer?
- 1
Upload your image
Drag and drop any image file, or click to browse. The current dimensions load automatically as the starting width and height.
- 2
Choose pixels or percent
Pick "Pixels" to type an exact target width and height, or "Percent" to scale relative to the original size — for example, 50% halves both dimensions.
- 3
Lock or unlock the aspect ratio
Leave it locked to resize proportionally with no distortion. Unlock it only if you deliberately need to stretch the image to an exact width and height that doesn't match its original ratio.
- 4
Pick the output format and quality
Choose JPG, PNG or WebP for the result. PNG has no quality setting since it is lossless; JPG and WebP use a 10–100% quality slider.
- 5
Resize and download
Click Resize image, check the new dimensions and file size, then download the result.
How is image resizer calculated?
Locked: new height = new width ÷ (original width ÷ original height). Unlocked: new width and new height are set independently.Where:
- original width, original height
- The source image's pixel dimensions, loaded automatically when you upload it
- aspect ratio
- original width ÷ original height — held constant when the lock is on
- new width, new height
- Your target pixel dimensions, or the original dimensions scaled by your chosen percentage
The simple version
With the aspect ratio locked, this is simple proportional scaling — think of it like resizing a photo by dragging a corner handle, where the shape never changes, only the size. Type a new width and the height follows automatically to keep the same proportions, and vice versa. Unlock it and you're setting width and height independently, which stretches the image to fit exactly — the image content itself gets squeezed or spread to match, which is only visually correct if the new box happens to share the original's aspect ratio.
What does it look like in practice?
Shrinking a phone photo for the web
Input
4032×3024 JPEG, resized to width 1200 with aspect ratio locked
Result
1200×900, file size drops from 4.1 MB to roughly 280 KB at quality 85
Locking the aspect ratio means height (900) is calculated automatically from the new width — no manual math needed, and no distortion.
Scaling by percentage
Input
2000×1500 PNG, percent mode set to 25%
Result
500×375
Percent mode is useful when you want a proportional reduction — "a quarter the size" — without calculating the exact target pixels yourself.
Stretching to fill a fixed banner slot
Input
1600×900 photo (16:9), width set to 1200 and height set to 400 with the lock off
Result
1200×400, visibly stretched vertically compressed
Unlocking the aspect ratio to hit an exact box size distorts anything that doesn't already match that ratio — 1600×900 is 16:9, but 1200×400 is 3:1, so the image is squeezed. Crop to 3:1 first if you want it to fill the slot without warping.
How accurate is it?
Resizing draws the source image onto a canvas at the target pixel dimensions using the browser's high-quality image smoothing (imageSmoothingQuality: "high"), then encodes the result to your chosen format. The dimensions and file size shown after resizing are exact, taken from the actual output file.
- Enlarging an image beyond its original resolution does not add real detail — the canvas interpolates between existing pixels, which produces a softer, not sharper, result at large upscale factors.
- Choosing JPEG as the output format flattens any transparency onto solid white before resizing, since JPEG has no alpha channel — this happens regardless of whether the source was PNG or WebP.
- File size after resizing depends on both the new pixel count and the quality setting for JPG/WebP output — PNG output size is not directly controllable beyond the dimension change itself.
- There is no crop-to-fill or letterboxing mode — an unlocked aspect ratio stretches the image to the exact box you specify rather than cropping or padding it.
What should you know before using it?
How the two resize modes behave, and when to use each:
| Mode | Behaviour |
|---|---|
| Pixels, locked aspect ratio | Proportional scale. Set one dimension, the other follows automatically. Never distorts the image. |
| Pixels, unlocked aspect ratio | Stretches to the exact width and height you set. Distorts the image if the target ratio differs from the original. |
| Percent | Scales both dimensions by the same factor — always proportional, since width and height move together. |
| Output format: PNG | Lossless, no quality slider, keeps transparency. |
| Output format: JPG | Lossy with adjustable quality, transparency flattened to white. |
| Output format: WebP | Lossy with adjustable quality, keeps transparency. |
Which tools relate to the image resizer?
The image resizer is one of 31 image tools on this site. These are the ones most often used alongside it — either because they handle the next step in the same job, or because they answer a question this tool raises.
Image Crop
Use this first if you need to fill an exact aspect ratio without stretching — crop to the target ratio, then resize to the exact pixel dimensions you need.
Image Compressor
For the smallest possible file, resize down to the dimensions you actually display at, then compress the result further with a dedicated quality pass.
Favicon Generator
For website icons specifically, use the dedicated favicon tool — it outputs the full standard set of icon sizes at once rather than one resize at a time.
Compress JPEG
If your resized output is a JPG and still larger than you'd like, run it through here for further quality-based compression.
When should you use a image resizer?
Because the image resizer runs entirely in your browser, it suits work you would not want to hand to a third-party server — client files, unpublished drafts, anything under an NDA. These are the situations people reach for it in most often.
Preparing images for a website
Displaying a 4000px-wide photo in an 800px content column wastes bandwidth on pixels nobody sees. Resizing to the actual display width before uploading cuts load time directly.
Meeting a platform's exact dimension requirements
Social media profile photos, marketplace listings and ad platforms often specify exact pixel dimensions. Pixel mode with the aspect ratio unlocked hits those requirements precisely, when the source already has a compatible ratio.
Reducing email attachment size
A batch of full-resolution event photos resized to a reasonable width before attaching keeps a whole set under a mail provider's size cap.
Standardizing image sizes across a product catalogue
Resizing every product photo to the same target width keeps a store's image grid visually consistent.
Open the Standardizing image sizes across a product catalogueFrequently asked questions
How do I resize an image without distorting it?
What is the difference between resizing by pixels and by percent?
Does resizing an image reduce its file size?
Can I resize an image to a specific aspect ratio without cropping?
Will enlarging a small image make it look better?
What image formats can I export after resizing?
Is my image uploaded to a server when I resize it?
Is the image resizer safe to use?
This tool runs entirely inside your browser. Your text, files and settings are processed on your own device and are never uploaded to our servers — there is nothing for us to store, log or leak. You can confirm it yourself: open your browser DevTools, switch to the Network tab, and use the tool. You will not see an upload request. It also means the tool keeps working if your connection drops mid-task.
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